A cationic rhodium-chiral diene complex as a high-performance catalyst for the intramolecular asymmetric [4+2] cycloaddition of alkyne-1,3-dienes.-猫眼课题宝

DOI：

10.1002/anie.200702586

发表时间：

2007-09

期刊：

Angewandte Chemie

影响因子：

通讯作者：

中科院分区：

文献类型：

作者：

R. Shintani;Y. Sannohe;T. Tsuji;Tamio Hayashi

过渡金属催化的不对称转化反应的成功发展需要同时具有高的催化活性和高的对映选择性。因此，需要适当地评估在给定催化反应中催化剂活性与过渡金属上的配体的性质之间的关系，并通过使用具有高活性所需性质的手性配体来开发其不对称变体。在这种情况下，我们在本文中证明，铑-二烯配合物是更积极的比它的铑-双膦对应物作为分子内[4+ 2]环加成的炔醚化的1，3-二烯的催化剂，和使用的手性二烯配体导致该反应的高活性和对映选择性的不对称变体的发展。自从Livinghouse在1990年首次报道以来，[1]许多铑（I）配合物，沿着与其他几种过渡金属的配合物，[2]已经被证明可以催化炔系1，3-二烯的分子内[4+ 2]环加成反应。带有双膦配体如1，2-双（二苯基膦基）乙烷（dppe）[3]或1，4-双（二苯基膦基）丁烷（dppb）[4]的阳离子铑（I）配合物已被用作这些反应的高效催化剂，并且还开发了一些使用手性双膦配体的不对称变体。[5]Chung等人，另一方面，描述了[Rh（萘）（cod）] BF 4（cod= 1，5-环辛烯）作为有效催化剂的用途，[6]从而证明了无膦的铑-二烯络合物也可以对这些环加成显示出高活性。[7]在这些先例的基础上，我们最初专注于几种配体的头对头比较，以定量评估它们在铑催化的分子内[4+ 2]环加成反应中的效率，其中炔醚化的1，3-二烯1a作为模型底物[Eq.①]。这些反应在2mol%铑催化剂存在下在二氯甲烷中于258 ℃在反应量热计（Omnical SuperCRC）中进行，并且通过Blackmond开发的反应进程动力学分析方法分析数据。[8]由Rh-cod络合物催化的反应进行得非常快，仅在10分钟内就实现了97%的转化率（图1）。相比之下，使用铑-双膦催化剂得到慢得多的反应（10分钟后转化率为3-4%），从而确定在这些条件下Rh-cod复合物的活性比其Rh-dppe和Rh-dppb对应物高至少20倍这些动力学研究的结果表明，使用手性二烯配体[9-12]对于开发该方法的高效不对称变体是期望的。[13]如反应式（2）所示，1a的反应以（S，S）-Ph-bod*[10]作为配体顺利进行，

The successful development of a transition-metal-catalyzed asymmetric transformation requires the achievement of both high catalytic activity and high enantioselectivity. It is therefore desirable to properly evaluate the relationship between the catalyst activity and the nature of a ligand on the transition metal in a given catalytic reaction, and develop its asymmetric variant by employing a chiral ligand with the required properties for high activity. In this context, we demonstrate herein that a rhodium–diene complex is much more active than its rhodium–bisphosphine counterpart as a catalyst for intramolecular [4+ 2] cycloadditions of alkynetethered 1, 3-dienes, and that the use of a chiral diene ligand leads to the development of a highly active and enantioselective asymmetric variant of this reaction. Since the first report by Livinghouse in 1990,[1] many rhodium (I) complexes, along with complexes of several other transition metals,[2] have been shown to catalyze intramolecular [4+ 2] cycloaddition reactions of alkyne-tethered 1, 3-dienes. Cationic rhodium (I) complexes bearing a bisphosphine ligand such as 1, 2-bis (diphenylphosphanyl) ethane (dppe)[3] or 1, 4-bis (diphenylphosphanyl) butane (dppb)[4] have been utilized as highly efficient catalysts for these reactions, and some asymmetric variants using chiral bisphosphine ligands have also been developed.[5] Chung et al., on the other hand, described the use of [Rh (naphthalene)(cod)] BF4 (cod= 1, 5-cyclooctadiene) as an effective catalyst,[6] thereby demonstrating that a phosphine-free rhodium–diene complex can also show high activity for these cycloadditions.[7] On the basis of these precedents, we initially focused on the head-to-head comparison of several ligands to quantitatively evaluate their efficiency in the rhodium-catalyzed intramolecular [4+ 2] cycloaddition reaction with alkynetethered 1, 3-diene 1a as a model substrate [Eq.(1)]. These reactions were carried out in the presence of 2mol% of rhodium catalyst in dichloromethane at 258C in a reaction calorimeter (Omnical SuperCRC), and the data were analyzed by the reaction progress kinetic analysis method developed by Blackmond.[8] The reaction catalyzed by the Rh–cod complex proceeded very fast, with 97% conversion being achieved in only 10 min (Figure 1). In contrast, the use of rhodium–bisphosphine catalysts gave much slower reactions (3–4% conversion after 10 min), thereby establishing that the Rh–cod complex is at least 20 times more active than its Rh–dppe and Rh–dppb counterparts under these conditions (Figure 1).The results of these kinetic studies suggested that the use of a chiral diene ligand [9–12] would be desirable for the development of a highly efficient asymmetric variant of this process.[13] As shown in Equation (2), the reaction of 1a proceeded smoothly with (S, S)-Ph-bod*[10] as the ligand to

A cationic rhodium-chiral diene complex as a high-performance catalyst for the intramolecular asymmetric [4+2] cycloaddition of alkyne-1,3-dienes.

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